Climate averages 1991–2020
San Juan weather
in December.
A hot, moderately wet month: the 11th warmest and the 4th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
December is a hot month in San Juan: daytime highs average 28.1°C and nights cool to about 22.1°C. By daytime temperature it is the 11th warmest of the 12 months.
Expect about 48 mm of rain on roughly 12 days, which makes December a moderately wet month (the 4th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 11 h 03 min on an average December day.
The nearest other city in this atlas is Bayamón (9 km away). In December its highs average 28.1°C, about as warm as San Juan, with 45 mm of rain.
Among the 7 cities listed in Puerto Rico, San Juan ranks joint 3rd of 7 for the warmest December highs and joint 4th of 7 for the driest December (rainfall, lowest first). The mean December high of those 7 cities is 28.1°C; San Juan is level with that mean.
From December to January, average highs fall by 0.2°C to 28.0°C, and monthly rainfall falls from 48 mm to 39 mm.
The annual picture
December in context
Monthly rainfall
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
San Juan climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 28.0°C21.5°C | 21.5°C | 39 | 10.4 | 11.211 h |
| February | 28.6°C21.3°C | 21.3°C | 29 | 7.7 | 11.512 h |
| March | 29.3°C21.5°C | 21.5°C | 39 | 8.4 | 12.012 h |
| April | 30.0°C22.3°C | 22.3°C | 72 | 11.0 | 12.613 h |
| May | 30.4°C23.4°C | 23.4°C | 112 | 16.1 | 13.013 h |
| June | 31.3°C24.3°C | 24.3°C | 68 | 13.8 | 13.213 h |
| July | 31.5°C24.6°C | 24.6°C | 80 | 16.4 | 13.113 h |
| August | 31.5°C24.7°C | 24.7°C | 95 | 18.7 | 12.813 h |
| September | 31.2°C24.5°C | 24.5°C | 131 | 20.8 | 12.312 h |
| October | 30.4°C24.1°C | 24.1°C | 124 | 20.5 | 11.712 h |
| November | 28.9°C23.2°C | 23.2°C | 112 | 18.2 | 11.311 h |
| December, selected | 28.1°C22.1°C | 22.1°C | 48 | 12.2 | 11.011 h |
Rainfall is the average of the 30 separate monthly totals. A rain day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
December in nearby cities
- Bayamón in DecemberPuerto Rico · 9 kmHigh 28.1°C · Low 22.2°C · 45 mm rain
- Carolina in DecemberPuerto Rico · 18 kmHigh 27.9°C · Low 22.4°C · 48 mm rain
- Caguas in DecemberPuerto Rico · 27 kmHigh 27.4°C · Low 22.4°C · 58 mm rain
- Arecibo in DecemberPuerto Rico · 64 kmHigh 28.3°C · Low 22.1°C · 48 mm rain
- Ponce in DecemberPuerto Rico · 75 kmHigh 28.0°C · Low 22.3°C · 28 mm rain
- Mayagüez in DecemberPuerto Rico · 113 kmHigh 29.0°C · Low 23.5°C · 18 mm rain
- Punta Cana in DecemberDominican Republic · 243 kmHigh 26.5°C · Low 24.3°C · 52 mm rain
- Salvaleón de Higüey in DecemberDominican Republic · 275 kmHigh 27.3°C · Low 22.3°C · 37 mm rain
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsHow these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for San Juan) is explained once on the San Juan year overview and on the Sources, method and limits page.
Carolina lies in the same rainfall cell, so its rainfall figures are identical to these; temperatures differ because they come from smaller 0.1° cells.